Encoded information reading system including RFID reading device having multiple antennas

ABSTRACT

An encoded information reading (EIR) system can comprise a microprocessor, a memory, and at least one RFID reading device, all communicatively coupled to a system bus. The EIR system can further comprise two or more external antennas electrically coupled to a multiplexing circuit. The multiplexing circuit can be configured to electrically couple each antenna to the RFID reading device by using a time division method or a frequency division method. The external antennas can be disposed according to a spatial pattern configured to provide a spatially continuous RFID signal reception within a pre-defined area or volume. The antennas can be configured to receive RFID signals from a plurality of RFID tags attached to a plurality of items and disposed within a radio frequency range of the antennas. The EIR system can be configured to store in its memory a plurality of responses received from the plurality of RFID tags.

CROSS-REFERENCE TO RELATED APPLICATION

This is a Continuation of application Ser. No. 13/350,970 filed Jan. 16,2012. The disclosure of the prior application is hereby incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The invention is generally related to encoded information reading (EIR)systems and is specifically related to EIR systems includingradio-frequency identifier (RFID) reading devices.

BACKGROUND OF THE INVENTION

RFID methods are widely used in a number of applications, includingsmart cards, item tracking in manufacturing and retail, etc. An RFID tagcan be attached, e.g., to an inventory item. An EIR system can beequipped with an RFID reader to read the memory of an RFID tag attachedto an inventory item.

SUMMARY OF THE INVENTION

There is provided an encoded information reading (EIR) system comprisinga microprocessor, a memory, and at least one RFID reading device, allcommunicatively coupled to a system bus. The EIR system can furthercomprise two or more external antennas electrically coupled to amultiplexing circuit via coaxial cables. The multiplexing circuit can beconfigured to electrically couple each antenna to the RFID readingdevice by using a time division method or a frequency division method.The external antennas can be disposed according to a spatial patternconfigured to provide a spatially continuous RFID signal receptionwithin a pre-defined area or volume. The antennas can be configured toreceive RFID signals from a plurality of RFID tags attached to aplurality of items and disposed within a radio frequency range of theantennas. The EIR system can be configured to store in its memory aplurality of responses received from the plurality of RFID tags.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more embodiments of the invention. However, it should beunderstood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 schematically depicts a component-level diagram of one embodimentof the EIR system;

FIG. 2 schematically illustrates one embodiment of a switching algorithmthat can be used by an antenna multiplexing circuit;

FIG. 3 schematically depicts one embodiment of a data collection systemcomprising the EIR system;

FIGS. 4a, 4b, 5a, 5b, 5c, 6a, 6b, 7a, 7b, 8a, and 8b illustrate variousembodiments of multiple cell metamaterial (MTM) antennas.

The drawings are not necessarily to scale, emphasis instead generallybeing placed upon illustrating the principles of the invention. In thedrawings, like numerals are used to indicate like parts throughout thevarious views.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, there is provided an encoded information reading(EIR) system comprising at least one radio frequency identifier (RFID)reading device. The RFID reading device can be configured to read and/ormodify a memory of an RFID tag containing an encoded message. The RFIDreading device can be further configured to output decoded message datacorresponding to the encoded message.

The EIR system can further comprise two or more antennas and amultiplexing circuit configured to electrically couple each antenna tothe RFID reading device. In one embodiment, the multiplexing circuit canbe configured to alternatively couple each antenna to the RFID readingdevice by implementing a time division technology, so that during agiven time slot not more than one antenna of the plurality of antennasis coupled to the RFID reading device. In another embodiment, themultiplexing circuit can be configured to couple each antenna to theRFID reading device by implementing a frequency division technology, asdescribed in details herein infra. Various embodiments of the EIR systemcan be used in a numerous applications, including but not limited to,item tracking in manufacturing and retail, real-time inventory controlsystems, etc.

Item tracking and/or inventory control can be implemented by placing anRFID tag on each inventory item. Two or more antennas can be disposedthroughout a manufacturing, retail, storage or other facility. Thecombined reception area of the two or more antennas can be representedby a 2D area or a 3D volume, and can be designed to provide spatiallycontinuous RFID signal reception within the facility. In one embodiment,two or more antennas can be installed on two or more shelves within awarehouse. In another embodiment, two or more antennas can be installedin a vending machine.

Two or more antennas can transmit and receive radio frequency (RF)signals to and from multiple RFID tags attached to inventory items. AnRFID tag can store the tag identifier in its memory. An RFID tagattached to an inventory item can further store in the tag's memory aproduct code of the item, an EPC code of the item, and/or at least onealphanumeric string identifying the item.

The RFID reading device can be configured to output decoded message datacontaining, for example, identifiers of the items to which the RFID tagsare attached. The EIR system can be configured to store in its memoryand/or transmit to an external computer the item identifiers receivedfrom the plurality of RFID tags.

Component-level diagram of one embodiment of the EIR system is now beingdescribed with references to FIG. 1. EIR system 100 can comprise atleast one microprocessor and a memory 120, both coupled to the systembus 170. The microprocessor can be provided by a general purposemicroprocessor or by a specialized microprocessor (e.g., an ASIC). Inone embodiment, the EIR system 100 can comprise a single microprocessorwhich can be referred to as a central processing unit (CPU). In anotherembodiment, the EIR system 100 can comprise two or more microprocessors,for example, a CPU providing some or most of the EIR systemfunctionality and a specialized microprocessor performing some specificfunctionality. A skilled artisan would appreciate the fact that otherschemes of processing tasks distribution among two or moremicroprocessors are within the scope of this disclosure.

The EIR system 100 can further comprise a communication interface 140communicatively coupled to the system bus 170. In one embodiment, thecommunication interface can be provided by a wireless communicationinterface. The wireless communication interface can be configured tosupport, for example, but not limited to, the following protocols: atleast one protocol of the IEEE 802.11/802.15/802.16 protocol family, atleast one protocol of the HSPA/GSM/GPRS/EDGE protocol family, TDMAprotocol, UMTS protocol, LTE protocol, and/or at least one protocol ofthe CDMA/1×EV-DO protocol family.

The EIR system 100 can further comprise one at least one RFID readingdevice 133. In one embodiment, the RFID reading device 133 can beconfigured to read a memory of an RFID tag containing an encoded messageand to output raw message data containing the encoded message. Inanother embodiment, the RFID reading device 133 can be configured toread a memory of an RFID tag containing an encoded message and to outputdecoded message data corresponding to the encoded message. As usedherein, “message” is intended to denote a character string comprisingalphanumeric and/or non-alphanumeric characters. An encoded message canbe used to convey information, such as identification of the source andthe model of a product, for example, in a UPC code.

The EIR system 100 can further comprise two or more external antennas155 a-155 z. Each antenna can be electrically coupled via a coaxialcable to a multiplexing circuit 150. The multiplexing circuit 150 can beconfigured to couple each antenna to the RFID reading device 133.

In one embodiment, the multiplexing circuit can be configured toalternatively couple each antenna to the RFID reading device byimplementing a time division technology, so that during a given timeslot not more than one antenna of the plurality of antennas is coupledto the RFID reading device. In a further aspect, the multiplexingcircuit 150 can implement a round robin algorithm schematically shown inFIG. 2. The multiplexing circuit 150 can select an antenna pointed to bya counter 212 from a list 220, increment the counter 212, and return thecounter to the beginning of the list 220 if the end of the list isreached. The selected antenna can be electrically coupled to the RFIDreading device 133 for a pre-defined period of time, and then the nextantenna can be selected from the list. In one embodiment, themultiplexing circuit 150 can be configured to switch to the next antenna155 a-155 z responsive to establishing that the RF signal strength fromthe currently connected antenna is below a pre-defined threshold.

In another embodiment, the multiplexing circuit 150 can be configured tocouple each antenna to the RFID reading device by implementing afrequency division technology. The distance between the antennas canexceed the effecting RF signal reception range by each antenna, andhence two or more antennas can transmit or receive two or more RFsignals simultaneously. In order to distinguish the two or more RFsignals within the RFID reading device, the signals received by eachantenna can be frequency-shifted up or down by the multiplexing circuit150 before feeding the signal into the RFID reading device, and signalsto be transmitted by each antenna can be frequency-shifted up or down bythe multiplexing circuit 150 before feeding the signals into thetransmitting antenna, so that non-overlapping frequency ranges areassigned by the multiplexing circuit 150 to each antenna signals withinthe RFD reading device.

In a further aspect, the multiplexing circuit 150 can be implemented inhardware, software, or using both hardware and software components.

In one embodiment, the EIR system 100 can further comprise a softwaremodule for processing the data received from the plurality of RFID tags.

In one embodiment, the EIR system 100 can further comprise a displayadapter 175 and a keyboard 179 allowing an operator of the EIR system100 to select and visualize the data received from the plurality of RFIDtags.

In one embodiment, the EIR system 100 can further comprise a powersupply 181 provided, e.g., by an AC converter and/or by a battery. Thecomponents of the EIR system 100 can be incorporated into a variety ofdifferent housings including a portable housing and a housing which canbe mounted on a fixed structure within a retail, manufacturing orstorage facility.

In one embodiment, the EIR system 100 can be configured to communicateto an external computer 171 as schematically shown in FIG. 3. The EIRsystem 100 can be communicatively coupled via the communicationinterface 140 to the network 110 a which, in turn, can becommunicatively coupled to one or more interconnected networks 110 b-110z. The external computer 171 can be communicatively coupled to thenetwork 110 c. The EIR system 100 can establish a communication sessionwith the external computer 171. In one embodiment, network frames can beexchanged by the EIR system 100 and the external computer 171 via one ormore routers, base stations, and other infrastructure elements. Inanother embodiment, the external computer 171 can be reachable by theEIR system 100 via a local area network (LAN). In a yet anotherembodiment, the external computer 171 can be reachable by the EIR system100 c via a wide area network (WAN). A skilled artisan would appreciatethe fact that other methods of providing interconnectivity between theEIR system 100 and the external computer 171 relying upon LANs, WANs,virtual private networks (VPNs), and/or other types of network arewithin the scope of this disclosure.

In one embodiment, the communications between the EIR system 100 and theexternal computer 171 can comprise a series of HTTP requests andresponses transmitted over one or more TCP connections. A skilledartisan would appreciate the fact that using other transport andapplication level protocols is within the scope and the spirit of theinvention.

In one embodiment, the external computer 171 can host an item trackingdatabase. At least one of the messages transmitted by the EIR system 100to the external computer 171 can include decoded message datacorresponding to, e.g., an RFID label attached to an inventory item. Forexample, an EIR system 100 can transmit a request to the host computerto modify the item location record responsive to detecting a new itemplaced within the manufacturing, retail, or storage facility.

In a further aspect, the MID reading device 133 can be compliant withEPC™ Class-1 Generation-2 UHF RFID Protocol for Communications at 860MHz-960 MHz by EPCglobal, commonly known as the “Gen 2” standard, whichdefines physical and logical requirements for a passive-backscatter,Interrogator-talks-first (ITF) RFID system operating in the 860 MHz-960MHz frequency range.

In one embodiment, the EIR system 100 can transmit information to apassive RFID tag by modulating an RF signal in the 860-960 MHz frequencyrange. An RFID tag can receive both information and operating energyfrom the RF signal transmitted by the EIR system 100. The EIR system 100can receive information from the RFID tag by transmitting acontinuous-wave (CW) RF signal to the MID tag. “Continuous wave” canrefer to any waveform transmitted by an RFID reading device and suitableto power a passive RFID tag, e.g., a sinusoid at a given frequency. TheRFID tag can respond by modulating the reflection coefficient of itsantenna, thus backscattering an information signal to the EIR system100. In one embodiment, the RFID tag can modulate the reflectioncoefficient of its antenna only responsive to receiving an RFID signalfrom the EIR system 100.

In a further aspect, the EIR system 100 can be configured to sendinformation to one or more MD tags by modulating an RF carrier usingdouble-sideband amplitude shift keying (DSB-ASK), single-sidebandamplitude shift keying (DSB-ASK), or phase-reversal amplitudeshift-keying (PR-ASK) using a pulse-interval encoding (PIE) format. RFIDtags can receive their operating energy from the same modulated RFcarrier.

In another aspect, the EIR system 100 can establish one or more sessionswith one or more RFID tags. An RFID tag can support at least onesession-dependent flag for every session. The session-dependent flag canhave two states. An RFID tag can invert a session-dependent flagresponsive to receiving a command from the EIR system 100. Tag resourcesother than session-dependent flags can be shared among sessions. Inanother aspect, an RFID tag can support a selected status flagindicating that the tag was selected by the EIR system 100.

Responsive to receiving an interrogation signal transmitted by the EIRsystem 100, an RFID tag can transmit a response signal back to the EIRsystem 100. The response signal can contain useful data, e.g., anElectronic Product Code (EPC) identifier, or a tag identifier (TID). Theresponse signal can include a representation of a binary string, atleast part of which is equal to at least part one of the specified oneor more target item identifiers.

In one embodiment, the EIR system 100 can implement EPC™ Class-1Generation-2 UHF RFID Protocol for Communications at 860 MHz-960 MHz byEPCglobal. The EIR system 100 can interrogate RFID tags using thecommands described herein infra.

Select command can be used by the EIR system 100 to select a particularRFID tag population for the subsequent inventory round. Select commandcan be applied successively to select a particular tag population basedon user-specified criteria. Select command can include the followingparameters:

-   -   Target parameter indicates whether Select command modifies a        tag's SL flag or Inventoried flag, and in the latter case it        further specifies one of four available sessions (S0, . . . ,        S3);    -   Action parameter indicates whether matching tags assert or        deassert SL flag, or set their Inventoried flag to A or B state;        tags conforming to the contents of MemBank, Pointer, Length, and        Mask parameters are considered to be matching;    -   Mask parameter contains a bit string that a tag should compare        to a memory location specified by MemBank, Pointer, and Length        parameters;    -   MemBank parameter specifies the memory bank to which Mask        parameter refers (EPC, TID, or User);    -   Pointer parameter specifies a memory start location for Mask;    -   Length parameter specifies the number of bits of memory for        Mask; if Length is equal to zero, all tags are considered        matching.

Inventory command set can be used by the EIR system 100 to single outone or more individual tags from a group. A tag can maintain up to foursimultaneous sessions and a binary Inventoried flag for each session.Inventory command set includes the following commands:

-   -   Query command can be used to initiate and specify an inventory        round; it contains a slot counter value (Q=0 to 15) determining        the number of slots in the round; the command also includes Sel        parameter specifying which tags should respond to the Query.    -   QueryAdjust command can be used to adjust the value of the tag's        slot counter Q without changing any other parameters;    -   QueryRep command can be used to repeat the last Query command;    -   Ack command can be used to acknowledge a tag's response;    -   NAK command can be used to force a tag to change its state to        Arbitrate.

An RFID tag can implement a state machine. Once energized, a tag canchange its current state to Ready. A selected tag can, responsive toreceiving Query command, select a random integer from the range of [0;2^(Q-1)]. If the value of zero is selected, the tag can transition toReply state, backscattering a 16-bit random number. If a non-zero valueis selected, the tag can load the selected random integer into its slotcounter and change its state to Arbitrate.

Responsive to receiving the tag transmission, the EIR system 100 canacknowledge it with Ack command containing the same random number.Responsive to receiving Ack command, the tag can change its state toAcknowledged and backscatter its protocol control (PC) bits, EPC andcyclic redundancy check (CRC) value. Unacknowledged tag can select a newrandom integer from the range of [0; 2^(Q-1)], load the value into itsslot counter, and change its state to Arbitrate. Responsive to receivingQueryAdjust command, a tag in the Arbitrate state should decrement thevalue of its slot counter and backscatter its protocol control (PC)bits, EPC and CRC value if its slot counter is equal to zero.

Responsive to receiving the tag's transmission of its PC, EPC and 16-bitCRC value, the EIR system can send a QueryAdjust command causing the tagto invert its Inventoried flag and to transition to Ready state.

Access command set can be used by the EIR system 100 for communicatingwith (reading from and writing to) a tag. An individual tag must beuniquely identified prior to access. Access command set includes thefollowing commands:

ReqRn command can be used by the EIR system 100 to request a handle froma tag; the handle can be used in the subsequent Access command setcommands. Responsive to receiving Req_RN commands, a tag returns a16-bit random integer (handle) and transitions from Acknowledged to Openor Secured state.

Read command can be used by the EIR system 100 to read tag's Reserved,EPC, TID and User memory;

Write command can be used by the EIR system 100 to write to tag'sReserved, EPC, TID and User memory;

Kill command can be used by the EIR system 100 to permanently disable atag;

Lock command can be used by the EIR system 100 to lock passwordspreventing subsequent read or write operations; lock individual memorybanks preventing subsequent write operations; permanently lock the lockstatus of passwords or memory banks;

Access command can be used by the EIR system 100 to cause a tag having anon-zero access password to transition from Open to Secured state.

A skilled artisan would appreciate the fact that other methods ofinterrogating RFID tags by the EIR system 100 are within the scope ofthis disclosure.

In a further aspect, at least one antenna 155 a-155 z can be provided bya metamaterial (MTM) antenna. Metamaterials are artificial compositematerials engineered to produce a desired electromagnetic behavior whichsurpasses that of natural materials. MTM-based objects can includestructures which are much smaller than the wavelength of electromagneticwaves propagating through the material. MTM technology advantageouslyallows for precise control of the propagation of electromagnetic wavesin the confines of small structures by determining the values ofoperating parameters which can include operating frequency, bandwidth,phase offsets, constant phase propagation, matching conditions, andnumber and positioning of ports.

In one aspect, an MTM antenna can be physically small as compared toother types of antennas: an MTM antenna can be sized, for example, onthe order of one tenths of a signal's wavelength, while providingperformance equal to or better than an antenna made of a conventionalmaterial and sized on the order of one half of the signal's wavelength.Thus, for a frequency range of 860 MHz-930 MHz, an MTM antenna can havea size of 33 mm or less.

The ability of an MTM antenna to produce a desired electromagneticbehavior can be explained by the fact that while most natural materialsare right-handed (RH) materials (i.e. propagation of electromagneticwaves in natural materials follows the right-hand rule for the trio (E,H, β), where E is the electrical field, H is the magnetic field, and βis the phase velocity) exhibiting a positive refractive index, ametamaterial due to its artificial structure can exhibit a negativerefractive index and follow the left-hand rule for the trio (E, H, β). Ametamaterial exhibiting a negative refractive index can be a pureleft-handed (LH) metamaterial by simultaneously having negativepermittivity and permeability. A metamaterial can combine RH and LHfeatures (Composite Right and Left Handed (CRLH) materials).

In one embodiment, antenna 155 a-155 z can be provided by a multiplecell MTM antenna shown in FIGS. 4a (top view) and 4 b (3D view). Antenna155 a-155 z can comprise one or more conductive cell patches 202 a-202 zthat can be mounted on a dielectric substrate, provided, for example, bya printed circuit board (PCB) 210. Conductive cell patches 202 a-202 zcan be spatially separated so that capacitive couplings between adjacentcell patches can be created. Also disposed on the dielectric substrate210 can a feed pad 214 that can be provided, e.g., by a metallic plateand can be connected to a conductive feed line 216. Conductive feed line216 can be provided, e.g., by metallic a strip. Conductive feed line 216can be located close but separately from conductive cell patches 202a-202 b. A skilled artisan would appreciate the fact that MTM antennashaving two or more conductive feed lines are within the scope of thisdisclosure. A ground plane can be provided by a metallic layer disposedon the bottom side of PCB 210 (not shown in FIG. 4a ). Each cell patchcan be connected to the ground plane by a via.

In one embodiment, antenna 155 a-155 z can be provided by a multiplecell MTM antenna shown in FIGS. 5a (top view), 5 b (bottom view), and 5c (3D view). Antenna 155 a-155 z can comprise one or more conductivecell patches 302 a-302 z that can be mounted on a dielectric substrate,provided, for example, by a printed circuit board (PCB) 310. Conductivecell patches 302 a-302 z can be spatially separated so that capacitivecouplings between adjacent cell patches can be created. Also disposed onthe top surface of dielectric substrate 310 can be a feed pad 314 thatcan be provided, e.g., by a metallic plate and can be connected to aconductive feed line 316. Conductive feed line 316 can be provided,e.g., by a metallic strip, and can be located close but separately fromconductive cell patches 302 a-302 z. A skilled artisan would appreciatethe fact that MTM antennas having one or more conductive feed lines arewithin the scope of this disclosure. At least one conductive feed linecan comprise a feed line tuner 322 provided by a conductive strip havinga curved line form or an open polygon line form. A feed line tuner canbe used to adjust resonant frequency of antenna 155 a-155 z as explainedherein infra.

In one embodiment, feed pad 314 can be electrically coupled to coaxialcable connector 315. In one embodiment, shown in FIG. 5c , coaxial cableconnector 315 can be connected from the bottom side of antenna 155 a-155z. In another embodiment, coaxial cable connector 315 can be connectedfrom a lateral side of antenna 155 a-155 z. In a yet another embodiment,feed pad 314 can be electrically coupled to a twisted cable.

Also disposed on the top surface of dielectric substrate 310 can be oneor more ground planes 312 a-312 z provided, e.g., by one or moremetallic plates.

One or more conductive cell patches 302 a-302 z can be connected by oneor more vias 342 a-342 z to one or more conductive via lines 352 a-352 zdisposed on the bottom surface of dielectric substrate 310. At least oneconductive via line 352 a-352 z can comprise a via line tuner 354 a-354z provided by a conductive strip having a curved line form or an openpolygon line form. A via line tuner can be used to adjust resonantfrequency of antenna 155 a-155 z as explained herein infra. Alsodisposed on the bottom surface of dielectric substrate 310 can be abottom ground plane 360.

In one embodiment, dielectric substrate 310 can have a folded planeform-factor, as shown in FIGS. 6a (3D view) and 6 b (side view). The gapbetween the two ends of the folded plane can be unfilled (air gap) orcan be filled with a dielectric material. The folded design canadvantageously offer extra air gap (or can be filled with othermaterial). In another aspect, due to the folded design, a multi-layerMTM design can be implemented without inter-connections.

In one embodiment, dielectric substrate 310 can have a curved planeform-factor, as shown in FIGS. 7a (3D view) and 7 b (side view). The gapbetween the two ends of the folded plane can be unfilled (air gap) orcan be filled with a dielectric material. A skilled artisan wouldappreciate the fact that MTM antennas mounted on dielectric substrateshaving a more complex form factors (e.g., a 3D surface) are within thescope of this disclosure. A curved surface can advantageously provideadditional tune to the antenna directivity. A more complicated 3Dsurface can be constructed by folding and wrapping on object having adesired shape, such as a cone.

In one embodiment, antenna 155 a-155 z can be provided by amushroom-shape MTM antenna shown in FIGS. 8a (top view) and 8 b (3Dview). In one embodiment, the gap between the feed line 602 and the toppatch 604 can form a capacitor (left-hand); the via between the toppatch 604 and the bottom ground 608 can form an inductance (left-hand).

In a further aspect, antenna 155 a-155 z can be broadband, ultrawideband(UWB), or multiband (MB). Antenna 155 a-155 z can be designed to supportthe desired functionality and characteristics. Antenna size, resonantfrequencies, bandwidth, and matching properties can be controlled bychanging the antenna design parameters including number and size ofcells, the gap between the cells, the gap between the feed line and thecells, the size (radius and height) and location of vias, the length andwidth of the feed line, the length and width of the via line, thematerial and thickness of the substrate, and various other dimensionsand layouts.

Antenna size and resonant frequency can be controlled by the patch shapeand size. Cell patches can have a rectangular, triangular, circular orother shape. The most efficient antenna area usage can be provided by arectangular shape. In a further aspect, the resonant frequency can besensitive to the via line length. To control the via line length, a vialine tuner can be provided having a straight line form, a curved lineform, or an open polygon line form. The via line length can be used toadjust resonant frequency due to its left hand inductive character. In afurther aspect, the resonant frequency can be sensitive to the feed linelength and the size of the gap between a feed line and a cell patch. Tocontrol the feed line length, a feed line tuner can be provided having astraight line form, a curved line form, or an open polygon line form.The feed line length can be used to adjust resonant frequency due to itsleft hand capacitive character. In a further aspect, the resonantfrequency can be sensitive to the thickness of the substrate on whichthe antenna components are disposed. The substrate thickness can rangefrom 0.1 mm to 150 mm depending upon the substrate material. Variousmaterials having different permittivity can be used, for example, butnot limited to, FR4 (ε_(r)=4.4), Getek (ε_(r)=4.0), Polyimide(ε_(r)=3.5), Polyester (ε_(r)=3.9), Arlon AD250 (ε_(r)=2.5), RT/duroid5880 (ε_(r)=2.2), etc.

In another aspect, an antenna can comprise a single cell or multiplecells. A multi-cell antenna can have a smaller resonant frequency shiftas compared to a single cell antenna, but also can have a higher peakgain due to a better beam concentration.

In another aspect, the antenna return loss can be controlled by theradius of one or more vias that connect the cell patches and the groundplane: vias having smaller radius can provide a better return loss.

While the present invention has been particularly shown and describedwith reference to certain exemplary embodiments, it will be understoodby one skilled in the art that various changes in detail may be affectedtherein without departing from the spirit and scope of the invention asdefined by claims that can be supported by the written description anddrawings. Further, where exemplary embodiments are described withreference to a certain number of elements it will be understood that theexemplary embodiments can be practiced utilizing less than the certainnumber of elements.

A small sample of systems methods and apparatus that are describedherein is as follows:

-   A1. An encoded information reading (EIR) system comprising:-   a microprocessor communicatively coupled to a system bus;-   a memory communicatively coupled to said system bus;-   at least one RFID reading device communicatively coupled to said    system bus;-   two or more external antennas, each antenna of said two or more    antennas being electrically coupled to a multiplexing circuit via a    coaxial cable;-   wherein said multiplexing circuit is configured to electrically    couple each antenna of said two or more antennas to said RFD reading    device by using one of: a time division method, a frequency division    method;-   wherein said external antennas are disposed according to a spatial    pattern configured to provide a spatially continuous RFID signal    reception within one of: a pre-defined area, a pre-defined volume;-   wherein said two or more antennas are configured to receive RFID    signals from a plurality of RFID tags disposed within a radio    frequency range of said two or more antennas, said RFID tags being    attached to a plurality of items; and-   wherein said EIR system is configured to store in said memory a    plurality of responses received from said plurality of RFID tags.-   A2. The EIR system of A1, wherein said multiplexing circuit is    configured to electrically couple each antenna of said two or more    antennas to said RFID reading device for a pre-defined period of    time in a pre-defined sequential manner.-   A3. The EIR system of A1, wherein said multiplexing circuit is    configured to shift a frequency of a first signal received by an    antenna of said two or more antennas before feeding said first    signal into said RFID reading device; and-   wherein said multiplexing circuit is further configured to shift a    frequency of a second signal to be transmitted by an antenna before    feeding said second signal to said antenna by said RFID reading    device.-   A4. The EIR system of A1, wherein said multiplexing circuit    comprises one or more hardware components.-   A5. The EIR system of A1, wherein said multiplexing circuit    comprises one or more software components.-   A6. The EIR system of A1, wherein said plurality of responses    received from said plurality of RFID tags include one of: a product    code, an EPC code, an RFID tag identifier, and an alphanumeric    string.-   A7. The EIR system of A1, wherein said two or more external antennas    are mounted on one or more storage shelves.-   A8. The EIR system of A1, wherein said two or more external antennas    are mounted on a vending machine.-   A9. The EIR system of A1, further configured to transmit to an    external computer at least one message based on said plurality of    responses received from said plurality of RFID tags.-   A10. The EIR system of A1, further comprising a software module for    processing data received from said plurality of RFID tags.-   A11. The EIR system of A1, wherein at least one antenna of said two    or more external antennas is fabricated of a material having a    composite right- and left-handed (CRLH) structure.-   A12. The EIR system of A1, wherein at least one antenna of said two    or more external antennas is mounted on a printed circuit board    (PCB).-   A13. The EIR system of A1, wherein at least one antenna of said two    or more external antennas is provided by at least one of: a patch    cell array comprising one or more patch cells, a patch cell stack    comprising two or more patch cells.

The invention claimed is:
 1. A system comprising: a radio frequencyidentification (RFID) reader; two or more antennas that are configuredto receive RFID signals indicative of a plurality of responses from aplurality of RFID tags, respectively, disposed within a radio frequencyrange of the two or more antennas, wherein a multiplexing circuitelectrically couples each antenna of the two or more antennas to theRFID reader so that each antenna of the two or more antennas areconfigured to communicate with the RFID reader at the same time, and,using frequency division multiplexing, each of the two or more antennas,operating in the radio frequency range, transmit and receive RF signalssimultaneously at different non-overlapping frequencies assigned by themultiplexing circuit, wherein, during said reception of said RF signals,the multiplexing circuit is configured to shift a frequency of a firstsignal, from the plurality of RFID tags, received by an antenna of thetwo or more antennas before feeding the first signal into the RFIDreader, and wherein, during said transmission of said RF signals, themultiplexing circuit is further configured to shift a frequency of asecond signal to be transmitted to at least one of the plurality of theRFID tags by the RFID reader via an antenna of the two or more antennasbefore feeding the second signal to the transmitting antenna.
 2. Thesystem of claim 1, wherein the two or more antennas that are separatedby a distance that exceeds an effecting RF signal reception range byeach antenna so that the two or more antennas can transmit or receivetwo or more RF signals simultaneously without interference.
 3. Thesystem of claim 1, wherein the multiplexing circuit comprises one ormore hardware components.
 4. The system of claim 1, wherein themultiplexing circuit comprises one or more software components.
 5. Thesystem of claim 1, wherein a plurality of responses received from theplurality of RFID tags include one of: a product code, an EPC code, anRFID tag identifier, and an alphanumeric string.
 6. The system of claim1, wherein the two or more antennas are mounted on one or more storageshelves.
 7. The system of claim 1, wherein the two or more antennas aremounted on a vending machine.
 8. The system of claim 1, furtherconfigured to transmit to an external computer at least one messagebased on a plurality of responses received from the plurality of RFIDtags.
 9. The system of claim 1, further comprising a software module forprocessing data received from the plurality of RFID tags.
 10. The systemof claim 1, wherein at least one antenna of the two or more externalantennas is fabricated of a material having a composite right- andleft-handed (CRLH) structure.
 11. The system of claim 1, wherein atleast one antenna of the two or more external antennas is mounted on aprinted circuit board (PCB).
 12. The system of claim 1, wherein at leastone antenna of the two or more antennas is provided by at least one of:a patch cell array comprising one or more patch cells, a patch cellstack comprising two or more patch cells.
 13. The system of claim 1,wherein the two or more antennas are disposed according to a spatialpattern configured to provide a spatially continuous RFID signalreception within an area.
 14. A method comprising: receiving radiofrequency identification (RFID) signals, at two or more antennas,indicative of a plurality of responses from a plurality of RFID tags,respectively, disposed within a radio frequency range of the two or moreantennas; electrically coupling, by a multiplexing circuit, each antennaof the two or more antennas to an RFID reader so that each antenna ofthe two or more antennas are configured to communicate with the RFIDreader at the same time, and, using frequency division multiplexing,each of the two or more antennas, operating in the radio frequencyrange, transmit and receive RF signals simultaneously at differentnon-overlapping frequencies assigned by the multiplexing circuit; duringsaid reception of said RF signals, shifting a frequency of a firstsignal, from the plurality of RFID tags, received by an antenna of thetwo or more antennas before feeding the first signal into the RFIDreader; and during said transmission of said RF signals, shifting afrequency of a second signal to be transmitted to at least one of theplurality of the RFID tags by the RFID reader via an antenna of the twoor more antennas before feeding the second signal to the transmittingantenna.
 15. The method of claim 14, wherein the two or more antennasthat are separated by a distance that exceeds an effecting RF signalreception range by each antenna so that the two or more antennas can.16. The method of claim 14, wherein a plurality of responses receivedfrom the plurality of RFID tags include one of: a product code, an EPCcode, an RFID tag identifier, and an alphanumeric string.
 17. The methodof claim 14, wherein the two or more antennas are mounted on one or morestorage shelves.
 18. The method of claim 14, wherein the two or moreantennas are mounted on a vending machine.
 19. The method of claim 14,further comprising transmitting to an external computer at least onemessage based on a plurality of responses received from the plurality ofRFID tags.
 20. The method of claim 14, further comprising processingdata received from the plurality of RFID tags.